SegBoard / SideWay - self balancing two-wheeled skateboard

JasonDorieJasonDorie Posts: 1,930
edited 2015-03-18 (7:34 PM) in Robotics
This is still a work in progress, but it's far enough along to show it now.

It's a two-wheeled, self-balancing, electric "skateboard" thing. The brain is a Parallax Propeller (on a HoveryFly Gimbal board) running my latest Quaternion/DCM hybrid IMU code. It doesn't steer yet, but only because I haven't gotten to that part. There's no motor feedback either, so keeping it tracking straight is all done with the IMU - it adjusts the motor outputs to compensate for measured changes in heading.

Update: steering via Wii Nunchuk, and a power switch.

The frame parts all laid out prior to welding.
SegBoard-Frame.jpg


The underside of the board, showing the motors, gearing, chains, and the results of my horrible welding skills.
Segboard-Underside.jpg


The custom motor mount plates - my very first home-CNC'd aluminum parts.
SegBoard-MotorMounts.jpg


The HoverFly Gimbal board and the 2x32 Sabertooth motor controller.
SegBoard-Brains.jpg
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Comments

  • NWCCTVNWCCTV Posts: 3,629
    edited 2015-03-10 (4:39 PM)
    WOW!!! Way cool Jason. Can't wait to see it when it is done.
  • W9GFOW9GFO Posts: 4,005
    edited 2015-03-10 (9:21 PM)
    Looks like fun! Are you going to make it steer via leaning or a hand held controller, or something else??
  • JasonDorieJasonDorie Posts: 1,930
    edited 2015-03-10 (11:04 PM)
    I just got steering with a Wii Nunchuk controller working. I'll leave it like this for a bit to tune it, and I may be rebuilding the body. Eventually I'm hoping to use pressure sensors on the base, so putting more weight on one side will turn it, like a snowboard. I have no idea how well that'll work in practice though, so I wanted to go the easy route first.
  • JasonDorieJasonDorie Posts: 1,930
    edited 2015-03-11 (3:46 PM)
    Steering!

    I patched in to the I2C pins on the EEPROM, and the power / ground pins on the 3.3v regulator, added some hot glue for strain relief, and voila! I have steering. The Nunchuk now serves as both steering and the deadman switch. If you let go of the trigger button, or pull the cord, the board stops. A friend at work wanted to see it, so I took it for a spin through the office hallways.

    SegBoard-WiiChuk.jpg
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  • PublisonPublison Posts: 11,832
    edited 2015-03-11 (3:50 PM)
    Wow.!

    Saw you going sideways this morning, now your doing doughnuts.

    Great progress!

    Jim
  • Mark_TMark_T Posts: 1,981
    edited 2015-03-14 (9:04 AM)
    Neat - but I worry you will bend that frame as you don't have enough stiffness/strength in the direction that matters. Its
    hard to find room underneath, so I reckon strengthening spars welded on top across the middle would be possible.
    Or make it into a leaf spring and add bounce/suspension?
  • Duane DegnDuane Degn Posts: 10,400
    edited 2015-03-14 (10:00 AM)
    Very cool project!

    As you probably know, generic Nunchucks can vary greatly in quality. I'm guessing you're using an original Wii version.

    If you want to try a wireless Nunchuck, I recommend the ones made by Kama (or is it Nyko?). Both the joystick and the accelerometer appear to work well on the two I have.

    I hope you have some sort of error detection code to monitor for a disconnected Nunchuck.

    Again, super cool project. Thanks for posting.
  • JasonDorieJasonDorie Posts: 1,930
    edited 2015-03-16 (10:36 AM)
    Mark_T - It's hard to see, but there's a 3" wide strip of 1/4" plate welded across the bottom of the three square tubes. It's actually two chunks of thick 90 degree angle welded together, and that's what the wheels are mounted to. It's quite strong, and while I do worry that over time the welds will stress and crack, the plan has always been that this is a prototype and there will be another frame shortly. I want to shorten the board, widen the wheel stance, and maybe give them a bit of toe-in to help prevent wobble perpendicular to the wheels.

    Duane - It's an authentic Nintendo controller I've had in a box along with a Wiimote for a few years. I actually don't need to monitor for a disconnect, exactly. Since the trigger button has to be held for the board to run, a disconnect results in all 1 bits on I2C, and the Nunchuk button states are inverted, so a 1 bit means "button off". A cord pull has the same effect as releasing the button - the board stops running. The intention was to handle a disconnect properly, but I didn't end up needing to. I thought about getting a wireless one, but the cord pull actually works to my advantage.
  • xanaduxanadu Posts: 3,331
    edited 2015-03-16 (10:44 AM)
    Very cool and looks like a lot of fun! Most of all congrats on home CNC! Someday....

    Duane, that wireless nunchuck is just what I need!
  • egenrietheregenriether Posts: 29
    edited 2015-03-18 (7:34 PM)
    Awesome project, look forward to seeing it evolve. Keep us posted!
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